25 Pair Cat5e Backbone cable 1

[disinfo]

Hello,

When looking through a catalogue I noticed this cable for sale.

Can somebody explain to me how this is used in a data cabling enviroment.

I'm looking at upgrading some cab to cab links so that we can have at least 4Gbps running between them using 4x 1000Base-T links and port trunking on the switches.

Presumably you cannot use this cable for patch panel to patch panel links because you would end up with masses of exposed pairs.

Is it designed to be used with some kind of intemediary block such as a krone block?

Also, why 25 pairs? Obviously 25 / 4 gives you 6.25 so do you just discard one of the pairs?

Thanks in advance guys

Matt

 

[skip555]

fiber would be the way to go

the spare pair is a good point I assume since 25 pair is a telcom standard the manufacturers just stayed with it for 5e

66 blocks are cat5e rated so I would suppose 25 pair 5e plus 5e 66 blocks would give you a 25 pair cat5e backbone

why couldn't you use it patch panel to patch panel ?

I don't understand what you mean by "exposed pairs " keep in mind its the twist that need to be maintained within .5 inch of the termination not the cable sheath

I cant see any application where I would consider doing it

 

[disinfo]

Thanks for that.

In this case its going to have to be a copper link as there is no budget for extra switches and the existing ones are not fibre compatible.

The 25 pair cable just looked tempting for ease of installation, many of the cabs are in older parts of the building where installation can be difficult due to extremely messing electrical wiring.

I didn't realise that about the cable sheath, I thought the standards (EN50173 in my case) dictate that no more than 13mm of unsheathed cable is to be exposed.

I think i'll stick to standard cable in this case, but was curious to know how / where 25 pair cable fits in.

 

[skip555]

media converters aren't that much

in the patch panel price ballpark

 

[jeffy101]

the 25 pair cable was used back in the day. the phone companies would use the 25th pair as a centrex line so when techs were on site they could call back to central office. this was used before cell phones and such. thatis why most of our communications equipment comes in even numbered configs like 24 port digital card.

 

[oldtimerbob]

To tie between IDF(s)(as you are doing(cab to cab)), I would go ahead and use as many four pair cables as needed from panel to panel. The seath on the cable keeps the pairs twist ratio around one another to the point of termination and to undo it (as you would have to if you use the 25 pair) would undo the twist and have an effect on the performance (you would get cross talk,etc)and it would more than likely not pass a certification test.
Good Luck,



Has been in the cabling business for about twenty years and is now the Sr PM for a cabling company located in the Los Angeles area.

http://www.globusinc.net

Also a General Class Amatuer Radio Operator.

 

[LkEErie]

Wow, open up a "25 pair" cat 5e cable before you post. The last one I checked was really 6 4-pair cables and I don't recall what or if they did anything with the 25th pair.
Each cable pulls out of the sheath and, if you look at it closely, you can see the ridges of the paired cable. It's like they just sheathed 6 seperate cables.

LkEErie

 

[GFDANNHAUSER]

The reason for 25 pair is that you start duplicating amount of twists in the pairs, in a 25 pair cable no pair has the same amount of twists.

I did this cabling before, and it used to be AT&T wiring, now I think Bell that manufactures it.

It can be used for structured wiring using the AT&T wiring block, or patch panels.

G

 

[buitenhek]

Lkeerie has it right, 6 four pair cables plus 1 spare pair. Others above also state correctly the use by ATT for phone service and centrex last pair. The 25pair cable naturally evolved to CAT5e because... they could.
One difference today, the 6-4pair cables in the 25pair sheath are twisted strategically to reduce crosstalk. Much talk can be generated about waterfalling cable from an overhead to an MDF/IDF and the virtues of not perfectly aligning the cables.
Stepping Down Now - if you want to use the cable, great. It is a clean way to run 6 data/voice circuits.

Regards
Peter Buitenhek
ProfitDeveloper.com

"Never settle for a job well done...always look for cost cutting measures